System for controlling electormagnetic actuators

Abstract

A valve system ( 10 ) includes a piezoelectric transducer ( 44 ) mounted on its housing ( 16 ). To change the valve's state, a microcontroller ( 54 ) causes a valve driver ( 58 ) to drive current through the actuator's coil ( 12 ) at a relatively high level. It continues driving current through the coil ( 12 ) at the high level until the transducer's output reaches a magnitude characteristic of the disturbance that typically results when the actuator's armature ( 22 ) reaches the end of its travel. At that point, the microcontroller ( 54 ) reduces coil drive.

What is claimed is:  
     
         1 . An actuator system comprising: 
 A) an actuator including an armature and a coil operable by application of a coil drive thereto to conduct current and thereby tend to drive the armature to an end position from a rest position, to which the armature is biased to return in the absence of coil current;    B) a sound sensor so coupled to the actuator as to sense sound made by the armature in reaching the end position, the sound sensor generating a sensor output indicative of the sound that it senses; and    C) a control circuit operable to begin applying coil drive to the coil at a first level and responsive to the sensor output's meeting a predetermined end-position-indicating criterion to change the coil drive to a different level great enough to keep the armature from returning to the rest position.